The plot

On Halloween night in the small town of Wardenclyffe, Sonny and Sam accidentally release Slappy the Dummy after opening a manuscript they stumble upon in an abandoned house, which was previously owned by horror fiction writer R.L. Stine. Now the two boys, along with Sonny's sister Sarah and Stine himself, have to stop Slappy as the evil dummy and his Halloween monster friends are planning to create the Halloween Apocalypse.